The battle of the Schellenberg itself is rather more simple: the army composed of the Anglo-Dutch forces of John Churchill (the Duke of Marlborough, and great-great-great-great-relative of the other famous Churchill) and those of the Holy Roman Empire under Louis, Margrave of Baden, needs to get across the Danube and moves to do so at the town of Donauworth. The Bavarian army commanded by the Count d'Arco -that's a real title, despite the comic book villain overtones- wants to stop them, and decides to do that by parking itself just outside town on the Schellenberg, the tallest hill for miles.
Marlborough and Baden disagree over what to do, the englishman wanting to attack before more Bavarian reinforcements arrive, the german favouring taking things at a more measured pace. Since command is shared, there is no direct way for either of them to impose his will. However the solution comes from one of the charmingly weird practices of the time: Marlborough and Baden take turns to command the full army on alternate days. July 2nd, 1704 is Marlborough's turn in the seat, and he decides to push through with the attack. Baden goes along, presumably mumbling under his breath, and the two wings of the "Allied" army converge on Donauworth.
The Anglo-Dutch wing gets there first. Marlborough has formed an advance guard of roughly 15 battalions of infantry, and they deploy in the small valley below the Schlellenberg, while his artillery under Colonel Holcroft Blood (enough with the comic book names already) sets up outside the village of Berg and begins bombarding the Bavarian positions. Count d'Arco, who was not expecting an attack that day, hastily deploys his men behind the half-finished earthworks on the hill. A misunderstanding with the commander of the Donauworth garrison results in the fortifications between the hill and the city -and, indeed, the city's own outer fortifications- being left unoccupied (this is where an ominous chord would sound if this were an audio tape).
Almost at the same time as the lieutenant returns to report there's hardly any soldiers between the city and the Schellenberg, Louis of Baden arrives with his wing of the army. The Bavarians are still heavily engaged with the Anglo-Dutch wing, so d'Arco can spare only a few dragoons to shore up his exposed left. The commander at Donauworth appears to wake up to the situation, but the force he sends to defend the outer works is weak- the battalions have to deploy in two rather than the customary four ranks to cover the whole frontage.